Incursion takes a pretty simplistic approach to the borders.

Each tile is broken into 16x16-pixel subtiles (Incursion was designed prior to the new icon size stuff), and each potential grid intersection (offset from the subtile proper by 8 pixels diagonally) has bitflags indicating which parts belong to which territories. Essentially, a T-junction intersection can be three icons: One for the territory on one side, and one each for the ones in each corner.

Bit 0: Territory in NE
Bit 1: Territory in SE
Bit 2: Territory in SW
Bit 3: Territory in NW
Bits 4-5: Style (0-2)

Basically if any of the bits 0-3 are empty, the territory in that section belongs to whatever nearest bit was set counterclockwise. E.g., 5 means NE and SE are the same (bit 0 on, bit 1 off) and SW and NW are the same (bit 2 on, bit 2 off), so it's a vertical divider. The style number allows for one of three different graphic styles to be chosen at random. A non-intersection, belonging to all one territory, is always 0.

The icon format is [N].[B] or [N].b[B]. The number N is described above, but B is a number from 0-3 representing one of the bits, starting clockwise from NW rather than NE because apparently I did not think the system through well the first time. This says which of the territories this icon state belongs to; E.g., 5.0 means we're dealing with the territory that belongs to the northwest corner of a vertical divide. The lowercase b means this icon is a border icon, and has special highlighting.

There are some things I don't like about this format: It is still too blocky, and the icons only come in three limited flavors each. A more organic approach is possible now.

When Incursion starts up, it takes the icon file and does dome operations on it to create missing states (e.g., it does some rotations), then it does shifts so it has icons that are easier to work with in the 32x32 realm without using pixel offsets--because it was first written before pixel offsets. Territory icons are built as combinations of icon operations so that each should contain the exact states needed to show the territory, and Insert() is used so it can all be kept in a nice tight package.

A request: Please judge the cartridge classic entries by the end of 2011. =)